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Main task of an SHM system on a wind turbine is to detect defective developments at an early stage on all load-bearing components such as rotor blades or tower. This prevents damage and allows repair measures to be planned in time. But a vibrationbased SHM system can do much more! For example it can be used to detect incorrect pitch angle settings or imbalances and to monitor the loads acting on the system. Of course, additional sensors and algorithms are required for such additional functions of an SHM-System. The lecture reports on several years of experiments on a commercially operated wind turbine Nordex N117 with 2.4 MW nominal power provided with more than 100 additional sensors. This turbine is used as a research system. In detail, all 3 rotor blades were equipped with accelerometers, strain gauges, FBGs and gyroscopes. The nacelle was instrumented with temperature, acceleration and speed sensors at the fast shaft and the tower and foundation were provided with strain gauges and inclination sensors. For population monitoring, a wind farm with 8 turbines of the same type N117, also with a rated output of 2.4 MW per turbine, was used. However, no additional sensors were installed on these wind turbines. Instead, the existing ice detection system IDD.Blade®, which is also based on acceleration measurements, was used. In addition, the SCADA data was analyzed. For the tests concerning mass imbalance, additional weights were fixed to the rotor blade, for the tests concerning aerodynamic imbalance, the pitch angles were shifted manually. For all other developments, the time-synchronous data recorded over several months was analyzed. The necessary algorithms for automated data analysis could be developed on the basis of the tests and the long-term measurement data. In addition, the dynamics of the wind turbines was investigated with simulations. |
